Adult teeth lack the ability to reconstruct and/or regenerate missing tissues. As a result tooth loss is currently being treated by a variety of traditional clinical therapies using prostheses and implants. However, these devices are incapable of replacing all the junctions of the original tooth, often fail overtime, and are incapable of undergoing remodeling. This proposal focuses on the possibility of using dental pulp cells to engineer biological tooth crowns consisting of odontoblasts secreting dentine and ameloblasts secreting enamel. As is true in many other organs, one of the major problems in reconstruction and/or regeneration of tooth structures is the lack of clearly identified progenitor cells from adult tissues that are able to replace or regenerate the effete of mature cells and structure. One successful approach in tissue engineering is to foster in stem cells the biological processes that occur during development. This approach has been successfully used in tissue engineering of the liver and hemopoetic cells. In addition, the potential of stem cells isolated from bone marrow stromal fibroblasts to promote bone regeneration is well-documented. Essential for application of this approach is the identification of donor stem cells and signaling molecules involved in their differentiation. Our approach is based on the current understanding of the molecular cascades involved in the initiation events of the developing murine tooth. We hypothesize that young dental pulp contains stem cells that can respond to inductive signals from odontogenic epithelium. Our specific aims are: 1) to study the response of young dental pulp to inductive signals from early odotogenic epithelium; 2) to examine the response of in vitro expanded pulp fibroblasts grown within gelatin sponges to the inductive signals from odontogenic epithelium; and 3) to determine whether growth factors can initiate events in pulp similar to those initiated by early dental epithelium that lead to the formation of enamel- and dentine-like structures. Demonstration that interactions of odontogenic epithelium with pulp cells can lead to the formation of "new" dental papillae that in turn can induce the formation of an enamel organ in the overlying epithelium will provide a major step in the goal of engineering human biological tooth crowns.